Extendible vehicle light mount

ABSTRACT

An extendible vehicle light mount comprising a boom pivotally connectible to the roof of a vehicle for pivotal movement between an elevated position and a retracted position and a light supporting arm pivotally connected to the boom. The boom is elevated by an appropriate linkage which also controls the angular position of the light supporting arm relative to the boom. The vehicle light mount is mounted on the vehicle so that the longitudinal axis of the boom is generally parallel to the longitudinal axis of the vehicle in the retracted position. A warning light is mounted on the light supporting arm so that the warning light is substantially elevated above the roof of the vehicle when the boom is in the elevated position.

United States Patent [191 Thomas EXTENDIBLE VEHICLE LIGHT MOUNT [76]Inventor: Robert E. Thomas, 1323 N.

Spurgeon St., Santa Ana, Calif. 92701 22 Filed: July 21,1972 21Appl.No.:273,729'

[52] US. Cl. 240/57, 240/7.1 R, 240/49, 340/87 {51] Int. Cl. 360g l/00[58] Field of Search 240/57, 52 R, 7.1 E, 240/7.1 R, 3, 49; 182/2;340/87 [56] References Cited UNITED STATES PATENTS 3,579,184 5/1971Forestal 340/87 3,287,548 11/1966 Kompier 240/57 X 3,229,945 l/l966Hartman 240/57 X 2,616,768 11/1952 Stemm 182/2 3,480,109 11/1969 Eiteletal. 182/2 X 2.377.279 5/1945 Stewart 182/2 X 1 Jan. 1,1974

2,073,998 3/1937 Raby 182/2 X Primary Examiner-Richard L. MosesAttorney-Gordon L. Peterson [5 7] ABSTRACT An extendible vehicle lightmount comprising a boom pivotally connectible to the roof of a vehiclefor pivotal movement between an elevated position and a retractedposition and a light supporting arm pivotally connected to the boom. Theboom is elevated by an appropriate linkage which also controls theangular position of the light supporting arm relative to the boom. Thevehicle light mount is mounted on the vehicle so that the longitudinalaxis of the boom is generally parallel to the longitudinal axis of thevehicle in the retracted position. A warning light is mounted on thelight supporting arm so that the warning light is substantially elevatedabove the roof of the vehicle when the boom is in the elevated position.

14 Claims, 8 Drawing Figures EXTENDIBLE VEHICLE LIGHT MOUNT BACKGROUNDOF INVENTION Emergency vehicles, such as police cars, fire engines, andambulances, etc. are equipped with sirens and warning lights. Thiscombination of audio and visual stimuli is used to provide a warning ofthe approaching emergency vehicle.

In some instances, the ambient noise level makes the siren difficult tohear. For example, the noise of the car radio, the air conditioner, orof conversation within a vehicle may make it difficult or impossible forthe driver of that vehicle to hear the siren in sufficient time to takethe appropriate responsive action. Accordingly, much work has been doneto make the siren a more effective warning device.

The vehicle warning light provides a visual indication of the presenceof the emergency vehicle, and as such, it may be effective when thesiren is not. However, to be effective the warning light must be readilyvisible. Although the warning light is characteristically mounted on thetop of the emergency vehicle, it may be blocked from view by variousobstacles such as other vehicles, irregularities in the terrain, etc.

SUMMARY OF THE INVENTION The present invention makes the warning light amuch more effective warning device by enhancing the visibility thereof.This is accomplished by providing a vehicle light mount whichselectively elevates the light substantially above the roof of theemergency vehicle.

The vehicle light mount of this invention includes a boom pivotallyconnected to a support above the vehicle. The boom can be pivotedbetween an elevated position in which the boom projects upwardly fromits pivotal axis and a retracted position in which the boom liessubstantially along the roof of the vehicle. A light supporting arm ispivotally connected to the boom at a location remote from the pivotalaxis of the boom. A vehicle light is mounted on the light supportingarm. Accordingly, by pivoting of the boom to the elevated positionthereof, the warning light is elevated substantially above the roof ofthe vehicle. This makes the warning light visible from greater distancesand reduces the likelihood that the warning light will be blocked fromview by another vehicle or by irregular alarm.

On important advantage of the vehicle light mount of this invention isits simplicity. For example, only a single boom and light supporting armare required. The boom can advantageously include a channel so that, inthe retracted position, the channel forms the housing for substantiallyall of the vehicle light mount. This not only provides a pleasingappearnce, but eliminates the need for a separate container for thevehicle light mount.

The vehicle light mount is preferably oriented so that the longitudinalaxis of the boom is generally parallel to the longitudinal axis of thevehicle. With this orientation, the vehicle light mount affords theminimum amount of wind resistence to the vehicle movement when it is inretracted position. In addition, the wind load on the lightmount in theextended position can be more readily and sturdily accommodated than ifthe light mount were oriented transverse to the longitudinal axis of thevehicle.

The extended position of the boom may define a plurality of differentpositions or boom elevations. The

boom can be selectively raised to any one of these positions and,accordingly, the elevation of the warning light on the boom can beselected. The boom can be moved between the extended and. retractedpositions by a linkage. The linkage can be actuated hydraulically;however, in a preferred form of the invention, the linkage is actuatedby an electric motor.

Another advantage of this invention is that the linkage maintains thelight support arm and the warning light in a substantially horizontalposition as the boom is moved between the retracted and extendedpositions. By maintaining the warning light horizontal during thisinterval, the warning light may be fully used as the boom is beingpivoted and there is no accompanying loss of the effectiveness of thewarning light. In fact, the effectiveness of the warning light increasesas it is being elevated.

The vehicle light mount can advantageously include first and secondlinks pivotally connected to the support and to the boom, respectively,and means for pivotally interconnecting the links. The links form ascissors linkage which can be operated to raise and lower the boom. Thelinks can advantageously be operated by a nut and a screw with the screwbeing driven by an electric motor. In a preferred construction, the nutis attached to the links by pins which also pivotally interconnect thelinks. In the preferred embodiment, the nut and screw are in the form ofa ball screw actuator to reduce friction. The angular orientation of thelight supporting arm relative to the boom can be advantageouslycontrolled by a drive element which is pivotally connected to the lightsupporting arm and to one of the links. The invention also comprisesvarious structural features described more fully hereinbelow.

Another advantage of the present invention is that the boom and theassociated linkage may be utilized to elevate various devices toselected heights above a vehicle. For example, different kinds of lightsuch as flood lights or spot lights may be mounted on the lightsupporting arm. Furthermore, devices other than lights may be mounted onthe light supporting arm for elevation above the vehicle. For example, asign, fire hose, weapon, etc. may be mounted on the light supportingarm.

The invention can best be understood by reference to the followingdescription taken in connection with the accompanying illustrativedrawings.

BRIEF DESCRIPTION OF THE DRAWINGS "ible vehicle light in the retracted.position.

FIG. 4 is a sectional view taken generally along lines 4-4 of FIG. 3.

FIG. 5 is an enlarged, fragmentary sectional view taken generally alongline 5--5'of FIG. 4 and showing the connection between the nut of theball screw and the links.

FIG. 6 is an enlarged, fragmentary sectional view taken generally alonglines 6-6 of FIG. 4 showing the means for pivotally mounting the boom.

FIG. 7 is an enlarged sectional view taken generally along lines 77 ofFIG. 4 and illustrating the means for pivotally connecting the links andfor pivotally mounting the links.

FIG. 8 is an enlarged fragmentary sectional view taken generally alonglines 8-8 and showing the connection between the light supporting armand the boom and between the light supporting arm and the drive element.

DESCRIPTION OF THE PREFERRED EMBODIMENT FIGS. 1-3 show an extendiblevehicle light 11 mounted on an emergency vehicle 13 such as a policecar. Generally the extendible vehicle light 11 includes a base orsupport 15, a boom 17 pivotally mounted on the ebase, base, lightsupporting arm 19 pivotally connected to the outer end of the boom 17,and a warning light 21 suitably mounted on the light supporting arm 19.The boom 17 can be pivoted between a retracted position shown in FIG. 1and an extended position shown in FIG. 2 by boom operating means such asa scissors linkage 23 which is suitably driven as by a motor 25 and aball screw actuator 27. The angular orientation of the light supportingarm 19 is controlled by an elongated drive element 29 which is pivotallyconnected to the scissors linkage 23 and to the light supporting arm 19.

Turning now to a more specific description of the illustrated embodimentof the invention, the base is in the form of a plate which is spacedfrom a roof 30 of the emergency vehicle 13 by resilient mounts 31 whichmay be constructed of rubber or similar material. The base 15 isattached to the roof 30 in any suitable manner such as by threadedfasteners (not shown) which project through the base and the resilientmounts 31.

A boom mount 33 in the form of an upwardly opening channel is attachedto the base 15 by threaded fasteners 35 (FIG. 4) which project throughthe web or base of the channel which forms the boom mount. The boommount 33 has a pair of transversely spaced, upwardly extending flanges37 (FIGS. 2, 4, and 6).

The boom 17 includes a main channel 39 having interior mounting membersin the form of short angles 41 affixed thereto as by welding. The boom17 is pivotally connected to the flanges 37 by pins 43 (FIG. 6) whichextend through the flanges 37 and through one leg of each of the angles41. The pins 43 are held together as an assembly by a tube 45, and thepins are urged away from each other by a spring 47 carried by the tube.This connection allows the boom 17 to be removed from the flange 37 byurging the pins 43 toward each other against the biasing action of thespring 47. In addition, the main channel 39 conceals the pins 43.

Although the boom 17 could be constructed in different ways, in theembodiment illustrated, it includes the main channel 39 and an outerchannel 49 (FIG. 3). The main channel 39 opens downwardly and includesside walls 51 interconnected by web 53 (FIG. 6) and a pair of parallelledges 55 integral with and projecting inwardly from the side walls 51.A support member in the form of an angle 59 (FIG. 2) having a verticleleg and horizontal leg is affixed to the main channel 39 as by weldingand extends transversely thereto. The vertical leg of the angle 59 restson the ledges 55, and the horizontal leg of the angle 59 terminatesflush with the inner edges of the ledges 55. A gasket 60 (FIG. 7) isprovided between the main channel 39 and the support 15.

The outer channel 49 opens upwardly and is telescoped with the mainchannel 39. The outer channel 49 is affixed to the main channel 39 andto the angle 59 in any suitable manner such as by welding. The outerchannel 49 includes spaced, parallel flanges 61 interconnected by anintegral web 63.

The scissors linkage 23 includes a lower link 65 and an upper link 67(FIGS. 4, 5 and 7). The links 65 and 67 are substantially identical, andin the embodiment illustrated, each is in the form of an appropriatelyconfigured channel. The link 65 is pivotally connected by pin 69 to amounting bracket 71 which is affixed to the support 15 in any suitablemanner such as by threaded fasteners 73. Similarly, the upper link 67 ispivotally mounted by a pin 75 to a mounting bracket 77 which is suitablyconnected to the web 53 of the main channel 39. As seen in FIG. 7, thelower channel 65 opens upwardly and the upper channel 67 opensdownwardly.

The other ends of the links 65 and 67 may be pivotally interconnected inthe manner shown in FIG. 5. The lower link 65 has a pair of spacedparallel straps 79 suitably affixed to a web 81 thereof in spaced,paralleled relationship. A pair of pins 83 pivotally interconnect thelinks 65 and 67 by passing through the flanges of the two links and intothe straps 79.

The ball screw actuator 27 (FIGS. 2 and 5) which actuates the scissorslinkage 23 may be of conventional construction. The ball screw actuator27 includes a screw 85, a nut 87, and the usual balls (not shown) forproviding a driving relationship between the screw and nut.

The screw 85 and an externally threaded extension 88 of the nut 87project through an opening in a channel-shaped bracket 89 which ismounted on the pins 83 (FIG. 5). A nut 91 is mounted on the extension 88and the web of the bracket 89 is clamped between a nut 91 and the nut87. The nut 91 is locked against rotation relative to the nut 87 by asheet metal tab 93 which partially embraces the nut 91 at one end and isclamped between the nut 87 and the bracket 89 at the other end.

The motor 25 and the ball screw actuator 27 may be obtained as a unit. Amounting member 95 (FIG. 4) is connected at one end to the motor 25 andis pivotally connected at the other end to a downwardly opening channel97 which is affixed to an end wall 99 of the boom 17. Thus, the motor 25and the ball screw actuator 27 can pivot about a horizontal axis definedby a pin 101 which interconnects the mounting member 95 and the channel97.

Although the light supporting arm 19 can be of various constructions, inthe embodiment illustrated, it includes an upwardly opening channel 103,a downwardly opening channel (FIG. 8) and a plate 107 (FIG. 4). Theupwardly opening channel 103 is pivotally mounted on the outer channel49 by a pin 109 which projects through the flanges 61 of the outerchannel and the flanges of the upwardly opening channel 103. Thedownwardly opening channel 105 is suitably affixed to the web of thechannel 103 as by welding. The plate 107 is suitably affixed to andsupported by the channels 103 and 105 as shown in FIG. 4.

The light 21 is mounted on the plate 107 in any suitable manner. Thelight 21 may be of conventional design. For example, the light 21 may bea warning light of the type commonly found on the roof of police carsand similar emergency vehicles. As such, the light 21 preferablyincludes a rotating source of illumination therein.

To control the angular position of the light supporting arm 19, thedrive element 29 is pivotally connected as by pins 111 and 113 to theupper link 67 and the downwardly opening channel 105, respectively. Thedrive element 29 in the embodiment illustrated is in the form of a tube;however, obviously other constructions could be employed. As shown inFIG. 7, the drive element 29 lies substantially centrally within theboom 17 and the links 65 and 67 are offset from a central positionwithin the boom.

The vehicle light 11 can be mounted on the vehicle 13 in differentorientations. Preferably, however, the vehicle light 11 lies along thecentral longitudinal axis of the vehicle 13 with the boom projectingrearwardly of the vehicle from the pin 43 toward the light21 in theretracted position of the light.

To move the vehicle light 11 to the extended position (FIG. 2) asuitable switch (not shown) is closed to energize the motor 25. Themotor 25 rotates the screw 85 of the ball screw actuator 27 in adirection to cause the nut 87 to translate along the screw toward themotor 25. As the nut 87 is affixed to the pins 83 of the scissorslinkage 23, such movement of the nut 87 tends to extend or open thescissors linkage. This applies an upward force to the boom17 which thenpivots about its pivot pins 43 (FIG. 2, 4 and 6) toward the extendedposition.

As the boom 17 is pivoting between the retracted and extended positionsthereof, the drive element 29 maintains the plate 107 substantiallyhorizontal. However, as the boom 17 is pivoting clockwise about the pins43 (as viewed in FIG. 2), there is relative pivotal movement between thelight supporting arm 19 and the boom 17 about a pin 109. In the extendedposition shown in FIG. 2, the warning light 21 can be seen from a muchgreater distance than in the retracted position. In addition, the upperportions of the boom 17 are located to the rear of the light 21 so asnot to block the visibility of the light from the side or front. In theretracted position, the boom 17 provides the vehicle light 11 with astreamlined appearance.

Although an exemplary embodiment of the invention has been shown anddescribed, many changes, modifications and substitutions may be made byone having ordinary skill in the art without necessarily departing fromthe spirit and scope of this invention.

I claim:

1. An extendible vehicle light connectible to a vehicle comprising:

a boom;

means for mounting the boom on the vehicle for pivotal movement about afirst pivotal axis between an extended position in which the boomprojects upwardly from the first pivotal axis and a retracted positionin which the boom is lower than in said extended position;

first and second links pivotally connected to a sup-' port and to theboom, respectively; first means for pivotally connecting said links toeach other;

means for operating said links to drive the boom between said positionsthereof;

a light supporting arm;

a light mounted on the light supporting arm;

second means for pivotally connecting the light supporting arm and theboom whereby the light supporting arm and the boom can pivot relative toeach other; and

a drive element drivingly connected to one of said links and said lightsupporting arm whereby operation of said links causes said drive elementto pivot the light supporting arm about its pivotal axis whereby thelight can be put in. the desired attitude in the extended position ofthe boom.

2. An extendible vehicle light as defined in claim 3 wherein saidoperating means includes a ball screw actuator drivingly connected to atleast one of said links and a motor for driving saidball screw actuator.

3. An extendible vehicle light as defined in claim 1 wherein saidoperating means includes a nut coupled to said means for pivotallyconnecting said links, a screw received by said nut and cooperatingtherewith, and means for providing relative rotation between the nut andthe screw.

4. An extendible vehicle light as defined in claim 3 wherein said secondmeans for pivotally connecting includes at least one pin, saidextendible vehicle light including abracket for coupling the nut to thepin.

5. An extendible vehicle light as defined in claim 1 wherein said firstand second links are lower, and upper links, respectively, the driveelement being coupled to the upper link and the light supporting arm.

6. An extendible vehicle light as defined in claim 1 wherein saidoperating means includes a ball screw actuator drivingly connectedto atleast one of said links and a motor for driving said ball screwactuator, said boom including an elongated channel, said first andsecond links being lower and upper links, respectively, said driveelement being coupled to the upper link and the light supporting arm ina position to maintain the light supporting arm substantiallyhorizontally as the boom is moved from said retracted position to saidextended position. I i

7. An extendible support structure connectible to a vehicle comprising:

means defining a support attachable to the vehicle;

a boom; I

means for mounting the boom on the support for pivotal movement about afirst pivotal axis between an extended position in which the boomprojects upwardly from the first pivotal axis and a retracted positionin which the boom is lower than in said'extended position;

boom operating means pivotally connectibleto the support and drivinglycoupled to the boom for operating said boom; 6

means for driving said boom operating means to thereby drive the boombetween said positions thereof;

a supporting arm adapted to support an object;

means for pivotally connecting the supporting arm and the boom at alocation remote from said first pivotal axis whereby. the supporting armand the boom can pivot relative to each other; and

means coupled to said supporting arm for controlling the relativepivotal movement between the supporting arm and the boom, said meansincluding an elongated drive element coupled to said supporting arm andextending generally toward said first pivotal axis.

8. An extendible support structure as defined in claim 7 wherein saiddriving means includes a ball screw actuator drivingly coupled to saidboom operating means and a motor for driving the ball screw actuator.

9. An extendible vehicle light mount mountable on a vehicle comprising:

a boom;

means for mounting the boom on the vehicle for pivotal movement about afirst pivotal axis between an extended position in which the boomprojects upwardly from the first pivotal axis and a retracted positionin which the boom is lower than in the extended position;

drive means for moving the boom between said positions thereof;

a light supporting arm adapted to have a light mounted thereon; meansfor mounting said light supporting arm on said boom for pivotal movementabout a second pivotal axis whereby the boom and the light supportingarm can undergo relative pivotal movement;

means for relatively pivoting said light support arm and said boom aboutsaid second axis as said boom is being pivoted about said first axisbetween said positions thereof so as to cause the light and the arm toproject generally horizontally from the boom as the boom is moved fromsaid retracted position to said extended position; and

said boom being in the form of a single rigid arm and said lightsupporting arm being shorter than said boom and supported in cantileverfashion by said boom.

10. An extendible vehicle light mount comprising:

a vehicle;

a boom;

means for mounting the boom on the vehicle for pivotal movement about afirst pivotal axis between an extended position in which the boomprojects upwardly from the first pivotal axis and a retracted positionin which the boom is lower than in said extended position, said boomextending from the first pivotal axis toward the rear of the vehiclewhen the boom is in said retracted position;

drive means for pivoting the boom between said positions thereof;

a light supporting arm adapted to have a light mounted thereon;

means for pivotally connecting the light supporting arm and the boomwhereby the light supporting arm and the boom can pivot about a secondpivotal axis relative to each other, said light supporting armprojecting from said second axis thereof toward the front of thevehicle;

means for causing relative pivotal movement about said second axisbetween said light supporting arm and said boom to maintain said lightsupporting arm in the desired attitutde as said boom is pivoted aboutsaid first pivotal axis; and

said drive means including a linkage for pivoting said boom, saidlinkage being located rearwardly of said first axis.

11. An extendible vehicle light mount as defined in claim 10 whereinsaid axes are generally parallel to each other and generally transverseto the longitudinal axis of the vehicle.

12. An extendible vehicle light mount comprising: a vehicle; a boom;means for mounting the boom on the vehicle for pivotal movement about afirst pivotal axis between an extended position in which the boomprojects upwardly from the first pivotal axis and a retracted positionin which the boom is lower than in said extended position, said boomextending from the first pivotal axis toward the rear of the vehiclewhen the boom is in said retracted position; drive means for pivotingthe boom between said positions thereof; a light supporting arm adaptedto have a light mounted thereon; means for pivotally connecting thelight supporting arm and the boom whereby the light supporting arm andthe boom can pivot about a second pivotal axis relative to each other,said light supporting arm projecting from said second axis thereoftoward the front of the vehicle; means for causing relative pivotalmovement about said second axis between said light supporting arm andsaid boom to maintain said light supporting arm in the desired attitudeas said boom is pivoted about said first pivotal axis;-a.nd said boomincluding a channel opening downwardly in said retracted position of theboom. 13. An extendible vehicle light mount mountable on a vehiclecomprising:

a boom; means for mounting the boom on the vehicle for pivotal movementabout a first pivotal axis between an extended position in which theboom projects upwardly from the first pivotal axis and a retractedposition in which the boom is lower than in the extended position; drivemeans for moving the boom between said positions thereof; a lightsuppoting arm adapted to have a light mounted thereon; means formounting said light supporting arm on said boom for pivotal movementabout a second pivotal axis whereby the boom and the light supportingarm can undergo relative pivotal movement; means for relatively pivotingsaid light support arm and said boom about said second axis as said boomis being pivoted about said first axis between said positions thereof soas to cause the light and the arm to project generally horizontally fromthe boom as the boom is moved from said retracted position to saidextended position; and said last mentioned means including an elongateddrive element coupled to said light supporting arm adjacent one end ofthe drive element and means for mounting said drive element adjacent theother end thereof for pivotal movement relative to the vehicle when thelight mount is mounted on the vehicle 14. An extendible supportstructure as defined in claim 13 including means defining a supportattachable to the vehicle, a light mounted on the light supporting arm,and said drive means including boom operating means pivotallyconnectible to the support and drivingly coupled to the boom foroperating said boom and motor means for pivoting said boom operatingmeans to thereby drive the boom between said positions thereof.

1. An extendible vehicle light connectible to a vehicle comprising: aboom; means for mounting the boom on the vehicle for pivotal movementabout a first pivotal axis between an extended position in which theboom projects upwardly from the first pivotal axis and a retractedposition in which the boom is lower than in said extended position;first and second links pivotally connected to a support and to the boom,respectively; first means for pivotally connecting said links to eachother; means for operating said links to drive the boom between saidpositions thereof; a light supporting arm; a light mounted on the lightsupporting arm; second means for pivotally connecting the lightsupporting arm and the boom whereby the light supporting arm and theboom can pivot relative to each other; and a drive element drivinglyconnected to one of said links and said light supporting arm wherebyoperation of said links causes said drive element to pivot the lightsupporting arm about its pivotal axis whereby the light can be put inthe desired attitude in the extended position of the boom.
 2. Anextendible vehicle light as defined in claim 3 wherein said operatingmeans includes a ball screw actuator drivingly connected to at least oneof said links and a motor for driving said ball screw actuator.
 3. Anextendible vehicle light as defined in claim 1 wherein said operatingmeans includes a nut coupled to said means for pivotally connecting saidlinks, a screw received by said nut and cooperating therewith, and meansfor providing relative rotation between the nut and the screw.
 4. Anextendible vehicle light as defined in claim 3 wherein said second meansfor pivotally connecting includes at least one pin, said extendiblevehicle light including a bracket for coupling the nut to the pin.
 5. Anextendible vehicle light as defined in claim 1 wherein said first andsecond links are lower and upper links, respectively, the drive elementbeing coupled to the upper link and the light supporting arm.
 6. Anextendible vehicle light as defined in claim 1 wherein said operatingmeans includes a ball screw actuator drivingly connected to at least oneof said links and a motor for driving said ball screw actuator, saidboom including an elongated channel, said first and second links beinglower and upper links, respectively, said drive element being coupled tothe upper link and the light supporting arm in a position to maintainthe light supporting arm substantially horizontally as the boom is movedfrom said retracted position to said extended position.
 7. An extendiblesupport structure connectible to a vehicle comprising: means defining asupport attachable to the vehicle; a boom; means for mounting the boomon the support for pivotal movement about a first pivotal axis betweenan extended position in which the boom projects upwardly from the firstpivotal axis and a retracted position in which the boom is lower than insaid extended position; boom operating means pivotally connectible tothe support and drivingly coupled to the boom for operating said boom;means for driving said boom operating means to thereby drive the boombetween said positions thereof; a supporting arm adapted to support anobject; means for pivotally connecting the supporting arm and the boomat a location remote from said first pivotal axis whereby the supportingarm and the boom can pivot relative to each other; and means coupled tosaid supporting arm for controlling the relative pivotal movementbetween the supporting arm and the boom, said means including anelongated drive element coupled to said supporting arm and extendinggenerally toward said first pivotal axis.
 8. An extendible supportstructure as defined in claim 7 wherein said driving means includes aball screw actuator drivingly coupled to said boom operating means and amotor for driving the ball screw actuator.
 9. An extendible vehiclelight mount mountable on a vehicle comprising: a boom; means formounting the boom on the vehicle for pivotal movement about a firstpivotal axis between an extended position in which the boom projectsupwardly from the first pivotal axis and a retracted position in whichthe boom is lower than in the extended position; drive means for movingthe boom between said positions thereof; a light supporting arm adaptedto have a light mounted thereon; means for mounting said lightsupporting arm on said boom for pivotal movement about a second pivotalaxis whereby the boom and the light supporting arm can undergo relativepivotal movement; means for relatively pivoting said light support armand said boom about said second axis as said boom is being pivoted aboutsaid first axis between said positions thereof so as to cause the lightand the arm to project generally horizontally from the boom as the boomis moved from said retracted position to said extended position; andsaid boom being in the form of a single rigid arm and said lightsupporting arm being shorter than said boom and supported in cantileverfashion by said boom.
 10. An extendible vehicle light mount comprising:a vehicle; a boom; means for mounting the boom on the vehicle forpivotal movement about a first pivotal axis between an extended positionin which the boom projects upwardly from the first pivotal axis and aretracted position in which the boom is lower than in said extendedposition, said boom extending from the first pivotal axis toward therear of the vehicle when the boom is in said retracted position; drivemeans for pivoting the boom between said positions thereof; a lightsupporting arm adapted to have a light mounted thereon; means forpivotally connecting the light supporting arm and the boom whereby thelight supporting arm and the boom can pivot about a second pivotal axisrelative to each other, said light supporting arm projecting from saidsecond axis thereof toward the front of the vehicle; means for causingrelative pivotal movement about said second axis between said lightsupporting arm and said boom to maintain said light supporting arm inthe desired attitutde as said boom is pivoted about said first pivotalaxis; and said drive means including a linkage for pivoting said boom,said linkage being located rearwardly of said first axis.
 11. Anextendible vehicle light mount as defined in claim 10 wherein said axesare generally parallel to each other and generally transverse to thelongitudinal axis of the vehicle.
 12. An extendiblE vehicle light mountcomprising: a vehicle; a boom; means for mounting the boom on thevehicle for pivotal movement about a first pivotal axis between anextended position in which the boom projects upwardly from the firstpivotal axis and a retracted position in which the boom is lower than insaid extended position, said boom extending from the first pivotal axistoward the rear of the vehicle when the boom is in said retractedposition; drive means for pivoting the boom between said positionsthereof; a light supporting arm adapted to have a light mounted thereon;means for pivotally connecting the light supporting arm and the boomwhereby the light supporting arm and the boom can pivot about a secondpivotal axis relative to each other, said light supporting armprojecting from said second axis thereof toward the front of thevehicle; means for causing relative pivotal movement about said secondaxis between said light supporting arm and said boom to maintain saidlight supporting arm in the desired attitude as said boom is pivotedabout said first pivotal axis; and said boom including a channel openingdownwardly in said retracted position of the boom.
 13. An extendiblevehicle light mount mountable on a vehicle comprising: a boom; means formounting the boom on the vehicle for pivotal movement about a firstpivotal axis between an extended position in which the boom projectsupwardly from the first pivotal axis and a retracted position in whichthe boom is lower than in the extended position; drive means for movingthe boom between said positions thereof; a light suppoting arm adaptedto have a light mounted thereon; means for mounting said lightsupporting arm on said boom for pivotal movement about a second pivotalaxis whereby the boom and the light supporting arm can undergo relativepivotal movement; means for relatively pivoting said light support armand said boom about said second axis as said boom is being pivoted aboutsaid first axis between said positions thereof so as to cause the lightand the arm to project generally horizontally from the boom as the boomis moved from said retracted position to said extended position; andsaid last mentioned means including an elongated drive element coupledto said light supporting arm adjacent one end of the drive element andmeans for mounting said drive element adjacent the other end thereof forpivotal movement relative to the vehicle when the light mount is mountedon the vehicle
 14. An extendible support structure as defined in claim13 including means defining a support attachable to the vehicle, a lightmounted on the light supporting arm, and said drive means including boomoperating means pivotally connectible to the support and drivinglycoupled to the boom for operating said boom and motor means for pivotingsaid boom operating means to thereby drive the boom between saidpositions thereof.